Thin cementitious decking members

ABSTRACT

A thin cementitious decking member is described. The thin cementitious decking member can span and be attached to two or more support members. The thin cementitious decking member can include a binder and natural or artificial sands, stones, or other aggregates. The thin cementitious decking member should have a thickness no greater than 1 ¾″. The thin cementitious decking member can include pre-stressed tendons bonded to the thin cementitious member. The pre-stressed tendons can be tensioned to impose a longitudinal compressive force into a cross section of the member. In this manner, the thin cementitious member is capable of supporting weight over a span between the two support members greater than 4 times the width of the thin cementitious member.

RELATED APPLICATION DATA

This application claims the benefit of U.S. Provisional PatentApplication Ser. No. 61/866,359, field Aug. 15, 2013, which isincorporated by reference herein for all purposes.

FIELD OF THE INVENTION

This invention pertains to decking systems, and more particularly to acementitious decking member that can span long distances.

BACKGROUND OF THE INVENTION

Decking surfaces are made of various materials. Wood products areprevalent in residential and commercial construction. They requiremaintenance and coatings, and have a limited service life. Ipe or otherhard woods are used when more longevity and beauty is desired, but arecostly and require frequent maintenance. Increasing scarcity, increasingcost of natural lumber products and growing concern about theenvironment have led to the introduction of manufactured deckingproducts, consisting of various plastics, aluminum, fiber-cement board,and other materials. These products have mixed results in durabilityagainst UV exposure, freeze-thaw cycles, and other natural andartificial elements.

Available concrete pavers are relatively square in plan view and arecapable of supporting weight over a relatively short span (10 timestheir thickness). A substantial width to length ratio in plan view isrequired to adequately support loading; but spans are currently limitedto approximately the width of the member. In addition, concrete paversare generally at least 2″ thick. Although durable and attractive, theconcrete material is heavy and brittle and used in relatively smallpieces.

A new decking product that is attractive, long lasting, capable ofsupporting weight over a relatively long distance requiring fewersupporting members, and easily installed would be desirable andvaluable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary isometric view of a horizontal deck surface,according to an embodiment of the invention.

FIG. 2 a is a sectional view of one possible configuration of theinvention taken across the line 2-2 of FIG. 1.

FIG. 2 b is a sectional view of an alternate possible configuration ofthe invention taken across the line 2-2 of FIG. 1.

FIG. 2 c is a sectional view of an alternate possible configuration ofthe invention taken across the line 2-2 of FIG. 1.

FIG. 3 is a fragmentary isometric view of the configuration of theinvention as described in FIG. 2 a.

FIG. 4 a is a sectional view taken across the line 4-4 of FIG. 1 of apossible attachment of the invention to a supporting member.

FIG. 4 b is a sectional view taken across the line 4-4 of FIG. 1 of analternate possible attachment of the invention to a supporting member.

FIG. 5 is an isometric view of an attachment clip.

FIG. 6 a is a sectional view taken along 4-4 of FIG. 1 of an alternatepossible attachment of the invention to a supporting member.

FIG. 6 b is an isometric view of an edge attachment clip installed on amember as viewed in FIG. 6 a.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Considering FIG. 1, a horizontal surface is created with long thin andnarrow cementitious plank or board members (10) which span over orbetween joists support members (11) capable of supporting weight.Support members (11) can be wood, steel, concrete, or other materials.The span between support members (11) can preferably be 30″, but canrange to about 60″. The member (10) is capable of relatively long spansbetween support members (11) as much as 50 times the thickness of themember. The top surface (12) can be decorative and slip resistant.Considering FIGS. 2 a and 3, the cementitious plank or board member hastwo opposite lateral sides (14), a top side (12), and a bottom side(13). The member can be of various sizes. A preferred configuration canhave cross sectional dimension of 1⅜″ tall, by 7⅜″ wide. Cementitiousmembers can be made thin (no more than 1¾″ in thickness). Cementitiousmembers can be made in any length, but as lengths get longer, thecementitious members become more fragile to handle and install.Preferred lengths for manufactured boards can be 8′, 10′, and 12′lengths. The top surface (12) can be flat or slightly convex to shedwater. The lateral sides (14) can be perpendicular to the bottom side(13) or slightly beveled.

The thin cementitious member is pre-stressed with non-corrosive tendons(15). The tendons (15) are placed such that there are an equal number oftendons an equal distance above and below, and to the right and left of,the cross sectional center of mass (CM) of the member. Note that thecenter of mass of the member may or may not be at the same location asthe cross sectional center of area of the member, depending on thedensity of the cementitious material and the casting method. The tendonsare textured such that they continuously bond with the cementitiousmaterial, allowing the member to be cut without losing the pre-stress.

The tendons (15) are non-corrosive materials so that the ends do notrust, and they will not corrode under normal atmospheric conditions andcause interior or other degradation of the member. The pre-stress tendonmaterial is selected based on the ability to bond to the cementmaterial, and the ability to hold stress over time with little stressrelaxation. ⅛″ type 316 stainless steel type 7×7 RHL wire rope is usedin the preferred configuration, but it could be synthetic, carbon fiber,or other materials.

Tendons (15) are tensioned to impose a longitudinal compressive forceinto the cross section of the member from 400 lbs per square inch to1300 lbs per square inch, depending on the load carrying requirements ofthe member.

The tendon mechanically bonds to the cementitious material such that itsstress is transmitted to the cementitious material without slippage in arelatively short distance, preferably the thickness of the member orless.

Considering FIG. 3 specifically, reinforcing rods (16) can be placedperpendicular with the longitudinal tendons (15) if required, but islikely not necessary on narrow members with a cross section 1⅜″ tall by8″ wide or less. The rods can be of any desired material, includingpre-stressing or non-stressed tendons.

Considering FIGS. 2 a and 4 a, a continuous or non-continuous slot orvoid (23) that is approximately triangular or trapezoidal in crosssection (the slot can also be shaped like a dovetail) can be formed inthe bottom of the member, which can be used to attach the member to asupporting member with a clip or tab (22).

Considering FIG. 2 b, in an alternate configuration, multiple slots (23)that are approximately triangular or trapezoidal in cross section (orshaped like a dovetail) can be used in the member (10) and thepre-stressing tendons (15) can be placed in various configurations aslong as they are twice the tendon diameter or more from each other orthe nearest edge or opening.

Considering FIG. 2 c, in an alternate configuration, members can beconstructed with interior longitudinal voids (18) to reduce weight.

Considering FIGS. 4 a and 5, members can be fastened to a supportingmember with polyurethane or other adhesive (24). One or more slots (23)can receive a tab (22) made of non-corrosive material, nylon, stainlesssteel, carbon fiber, or other to fasten the member to a supportingmember (11). The slot (23) also aids air circulation, allowing thesupport member (11) to breathe if necessary. The tab (22) is designedsuch that its bearing points (25) are spaced away from the more fragileedges of the slot in the cementitious member so it will be less likelyto fracture or chip, even if the tab is installed in a non-perpendicularfashion. The tab can have guide slots (26) that position a screw orother fastener (27) so that it naturally applies downward pressureagainst the supporting member as it is tightened, and applies clampingforce between the board and its supporting member. The member can attachto the tab by sliding onto the tab: the member does not need to bepermanently secured to the supporting member (e.g., by a screw thatconnects the member to either the tab or the supporting member).

Considering FIG. 4 b specifically, grooves on the bottom surface (19)can be formed on the members to allow airflow if used on a wood or othersurface that needs air circulation. An alternate attachment method canconsist of a mechanical fastener (20), such as a screw, installedthrough a hole (21) provided in each lateral side of the cementitiousmember at predetermined longitudinal locations attached to thesupporting member (11).

Considering FIGS. 6 a and 6 b, in an alternate configuration, the member(10) is manufactured with a continuous groove (28) in the sides (14) ofthe member (10). The lower surface of the groove has an upper surface(29) and lower surface (30) creating a saw-tooth in the lower horizontalsurface of the groove. An attachment clip (31) has a lower approximatelyhorizontal leg (32) and a higher and longer opposing approximatelyhorizontal leg (33). The lower leg (32) fits into the lower saw tooth ofthe groove (30) on the member. The upper leg (33) sits on the uppersurface of the saw tooth (29) of the adjacent member. A spacer on theattachment clip (34) maintains a predetermined spacing between themembers and holds the attachment clip against the members. The edgeattachment clip (31) holds the members to the supporting member (11)with a fastener (35). When multiple members are placed in this manner,the attachment clips hold the members from movement in 3 directions.

Considering FIG. 2 a, a decorative slip-resistant texture can beimprinted on the member (10) by the mold surface. A textured anddecorative surface can be achieved on the top side (12) and lateralsides (14) of the member after the cementitious material has cured bymeans of abrasive blasting, high pressure water blasting, or acidetching, exposing the internal aggregate mixture of the cementitiousmaterial. The cementitious material can be colored with iron oxide orother pigments.

Material Used

The members are made of a cementitious material, made from natural orartificial sands, stones, and other aggregates, held together with abinder of Portland cement, various pozzolones and chemical admixtureswhich cures by a chemical hydration process between the cement andwater. Aggregates can be from recycled materials, glass, or other.Constituents are properly proportioned to create a strong interlockingmatrix.

An example of a wet cast mix design based on a 100 lb sample:

Type II or Type III white or gray Portland cement 13.5 lbs   Silica fumeor Blast Furnace Slag 4.5 lbs  Iron oxide or other color as requiredWater reducing admixtures as required Plasticizer as required Airentraining admixture as required Water  6 lbs Well graded sand less than⅛″ in size 31 lbs Coarse aggregate (¼″ to ⅜″ in size) 45 lbs

An example of a dry cast mix design based on a 100 lb sample

Type II or Type III white or gray Portland cement 17.6 lbs  Silica fumeor Blast Furnace Slag 5.9 lbs Iron oxide or other color as requiredWater reducing admixtures as required Plasticizer as required Airentraining admixture as required Water 4.5 lbs Well graded sand lessthan ⅛″ in size  36 lbs Additional Fine aggregate ⅛″ in size  36 lbs

Manufacturing Processes

The members can be made in a wet cast process (cementitious materialwill flow, water to cement ratio of 0.35 to 0.60). In this process, thetendons are stretched in a mold, and the cementitious material cast intoand mechanically consolidated into the mold. The cementitious materialthen cures to an appropriate amount (in the range of 2500 psicompressive strength). The curing (hydration process) can be acceleratedwith heat while holding the moisture in the freshly cast member (orsteam curing). Once the member has cured sufficiently (compressivestrength of 2500 psi), the tendons are released from their restraints,transferring stress to the cast member and placing it into compression.For thin members wet cast as described, it is likely that the aggregateswill settle in the casting process causing a variation in density of thematerial with the depth. To account for the variation in density, it islikely that tendons need to be set off-center (not at the center ofarea) to keep the member from warping. Air entraining and water reducingadmixtures can be used that aid in freeze-thaw resistance and strengthof the material.

The members can be made with only enough water to hydrate the cement(dry cast). In this case, material will not flow. Water-cement ratio canbe limited to 0.18 to 0.28. Since the cementitious material does notflow, dry casting requires compacting the uncured material into a formor mold under substantial force and vibration to consolidate the mix.Dry casting can result in higher strength, lower moisture absorptioncharacteristics, and a durable material. Tendons can be associatedcloser to the center of area of the member since there is less or nosettling of the aggregate in the process, and there is not the concernfor warping or distortion that can be associated with pre-stressing avery thin wet cast member. Members constructed with the dry cast processcan be finished similar to what was described in the wet cast process,but the aggregate size is smaller.

Having described and illustrated the principles of the invention withreference to illustrated embodiments, it will be recognized that theillustrated embodiments can be modified in arrangement and detailwithout departing from such principles, and can be combined in anydesired manner. And although the foregoing discussion has focused onparticular embodiments, other configurations are contemplated. Inparticular, even though expressions such as “according to an embodimentof the invention” or the like are used herein, these phrases are meantto generally reference embodiment possibilities, and are not intended tolimit the invention to particular embodiment configurations. As usedherein, these terms can reference the same or different embodiments thatare combinable into other embodiments.

Consequently, in view of the wide variety of permutations to theembodiments described herein, this detailed description and accompanyingmaterial is intended to be illustrative only, and should not be taken aslimiting the scope of the invention. What is claimed as the invention,therefore, is all such modifications as can come within the scope andspirit of the following claims and equivalents thereto.

1. A decking system, comprising: two support members; and a cementitiousmember spanning and attached to the two support members, thecementitious member including a binder and natural or artificial sands,stones, or other aggregates, the cementitious member have a length, awidth, and a thickness, the thickness of the cementitious member nogreater than 1¾″, the cementitious member including pre-stressed tendonsbonded to the cementitious member and tensioned to impose a longitudinalcompressive force into a cross section of the member, so that thecementitious member is capable of supporting weight over a span betweenthe two support members greater than 4 times the width of thecementitious member.
 2. A decking system according to claim 1, whereinthe cementitious member is capable of supporting weight over a spanbetween the two support members greater than 10 times the thickness ofthe cementitious member.
 3. A decking system according to claim 2,wherein the cementitious member is capable of supporting weight over aspan between the two support members of up to 50 times the thickness ofthe cementitious member.
 4. A decking system according to claim 1,wherein the pre-stressed tendons are made of a non-corrosive material.5. A decking system according to claim 4, wherein the pre-stressedtendons are made of a material drawn from a set consisting of stainlesssteel type wire rope, synthetic materials, or carbon fiber.
 6. A deckingsystem according to claim 1, wherein the pre-stressed tendons aretensioned to impose a longitudinal compressive force into the crosssection of the member of between and including 400 and 1300 pounds persquare inch (lb./in²).
 7. A decking system according to claim 1, whereinthe pre-stressed tendons are spaced equally above and below a center ofmass of the cementitious member.
 8. A decking system according to claim1, wherein the pre-stressed tendons are spaced equally to the right andleft of a center of mass of the cementitious member.
 9. A decking systemaccording to claim 1, wherein the cementitious member further includesperpendicular rods running perpendicular to the longitudinal tendons.10. A decking system according to claim 1, wherein the cementitiousmember further includes a slot for attaching the cementitious member toeach of the two support members using tabs, the tabs including an upperportion shaped to fit into the slot in the cementitious member.
 11. Adecking system according to claim 10, wherein a shape of a cross sectionof the slot is drawn from a set consisting of a triangle, a trapezoid,and a dovetail.
 12. A decking system according to claim 10, wherein thetabs include bearing points that extend to contact edges of the slot.13. A decking system according to claim 10, wherein the pre-stressedtendons are positioned within the cementitious member at least two timesthe diameter of the pre-stressed tendons from the slot.
 14. A deckingsystem according to claim 10, wherein the slot is positionedapproximately in the center of the cementitious member.
 15. A deckingsystem according to claim 10, wherein: the slot is a longitudinal grooveon at least one side of the cementitious member; and the cementitiousmember further includes a second longitudinal groove on the at least oneside of the cementitious member, the second longitudinal slot located atthe bottom of the cementitious member.
 16. A decking system according toclaim 15, wherein the tab includes a spacer to maintain a predeterminedspacing between the cementitious member and an adjacent cementitiousmember.
 17. A decking system according to claim 1, wherein thecementitious member includes a longitudinal void.
 18. A decking systemaccording to claim 1, wherein the cementitious member includeslongitudinal grooves to facilitate airflow between the cementitiousmember and the two support members.
 19. A decking system according toclaim 1, wherein the cementitious member is attached to the two supportmembers using a fastener drawn from a set consisting of glue and screws.20. A decking system according to claim 1, wherein the cementitiousmember is made using a wet cast process.
 21. A decking system accordingto claim 1, wherein the cementitious member is made using a dry castprocess.
 22. A cementitious member having a length, width, andthickness, comprising: a binder and natural or artificial sands, stones,or other aggregates; and pre-stressed tendons bonded to the cementitiousmember and tensioned to impose a longitudinal compressive force into across section of the member, so that the cementitious member is capableof supporting weight over a span between the two support members greaterthan 4 times the width of the cementitious member, the thickness of thecementitious member no greater than 1¾″, wherein the cementitious memberis designed to span and be attached to two support members.
 23. Acementitious member according to claim 22, wherein the cementitiousmember is capable of supporting weight over a span between the twosupport members greater than 10 times the thickness of the cementitiousmember.
 24. A cementitious member according to claim 23, wherein thecementitious member is capable of supporting weight over a span betweenthe two support members of up to 50 times the thickness of thecementitious member.
 25. A cementitious member according to claim 22,wherein the pre-stressed tendons are tensioned to impose a longitudinalcompressive force into the cross section of the member of between andincluding 400 and 1300 pounds per square inch (lb./in²).
 26. Acementitious member according to claim 22, further comprising a slot forattaching the cementitious member to each of the two support membersusing tabs.
 27. A cementitious member according to claim 26, wherein ashape of a cross section of the slot is drawn from a set consisting of atriangle, a trapezoid, and a dovetail.
 28. A cementitious memberaccording to claim 26, wherein the slot is positioned approximately inthe center of the cementitious member.
 29. A cementitious memberaccording to claim 26, wherein: the slot is a longitudinal groove on atleast one side of the cementitious member; and the cementitious memberfurther includes a second longitudinal groove on the at least one sideof the cementitious member, the second longitudinal slot located at thebottom of the cementitious member.
 30. A cementitious member accordingto claim 22, wherein the cementitious member includes longitudinalgrooves to facilitate airflow between the cementitious member and thetwo support members.
 31. A tab for connecting a cementitious member anda support member, comprising: means for attaching the tab to a supportmember; and a top portion with an approximately triangular shape, thetop portion designed to fit in a slot in the cementitious member.
 32. Atab according to claim 31, further comprising bearing points on the topportion of the tab that extend to contact edges of the slot in thecementitious member.
 33. A tab for connecting a cementitious member anda support member, comprising: means for attaching the tab to a supportmember; and a top portion including two approximately horizontal legs,the two approximately horizontal legs designed to fit in a longitudinalgroove in the cementitious member and a second longitudinal groove in anadjacent cementitious member.
 34. A tab according to claim 33, whereinthe tab includes a spacer to maintain a predetermined spacing betweenthe cementitious member and the adjacent cementitious member.